Method and composition for cleaning and maintaining water delivery systems

ABSTRACT

A sodium chlorite solution is admixed with a second solution containing an acid to make a reacted mixture. The reacted mixture is introduced into a water system, viz. a conduit in which water flows or a tank containing water. The reacted mixture is added to the water system to inhibit and/or eliminate bacterial fouling in the system, and/or inhibiting and/or removing mineral deposits from the system, and/or for reducing or eliminating microorganisms from the system. The second component is acidic enough to convert the sodium chlorite into chlorine dioxide while remaining unaffected in the reacted mixture and at the same time being a mineral antiscalant. Optimum conversion of the sodium chlorite component into active chlorine dioxide requires at least several minutes reaction time and, preferably, the use of a suitable catalyst, such as sodium molybdate.

RELATED APPLICATIONS

[0001] This application claims priority to provisional application Ser.No. 60/223,215, filed Aug. 4, 2000, and to provisional application Ser.No. 60/280,447, filed Mar. 29, 2001.

TECHNICAL FIELD

[0002] This invention relates to a method and composition for cleaningand maintaining water storage and/or distribution systems. Moreparticularly, it relates to the use of a reacted mixture of a sodiumchlorite solution and a second solution containing an acid forinhibiting and/or removing bacterial fouling an/or inhibiting and/orremoving mineral deposits, and/or eliminating microorganisms from waterstorage and/or distribution systems.

BACKGROUND OF THE INVENTION

[0003] Water is stored in reservoirs and tanks and is delivered byconduits to places where the water is used. Water storage and deliverysystems often become fouled and/or obstructed by mineral scale depositsand/or biological growths and/or bio-films. Irrigation systems used inthe agricultural industry can experience fouling that is so severe thatwater flow is reduced to a level where valuable crops receiveinsufficient watering and perish from dehydration.

[0004] There is a need for compounds that can be added to water storageand delivery systems for eliminating the mineral and biologicalsubstances that cause the obstructions and comprise the systems. Aprincipal object of this invention is to provide such a composition anda method of its use for cleaning and maintaining water delivery systems,including tanks, reservoirs and conduits.

[0005] There is also a need for an easily achieved on-site metering andmixing of the components of the composition and an easily achievedintroduction of the composition into the water delivery system. Anotherobject of the present invention is to fulfill this need.

BRIEF SUMMARY OF THE INVENTION

[0006] A basic aspect of the present invention is to admix a sodiumchlorite solution with a second solution containing an acid to make areacted mixture. A predetermined amount of this reacted mixture is thenintroduced into water in a water distribution system.

[0007] According to an aspect of the invention, the reacted mixture isintroduced into a water system to inhibit and/or eliminate bacterialfouling in the system. Another aspect of the invention is to introducethe activated mixture into to the water for inhibiting and/or removingmineral deposits from the system. Yet another aspect of the invention isto introduce the activated mixture into the water for eliminatingmicroorganisms from the system.

[0008] According to yet another aspect of the invention, the secondcomponent is acid enough to convert the sodium chlorite into chlorinedioxide while remaining unaffected in the reacted mixture and at thesame time being a mineral antiscalant. The second solution may be formedby adding PBTC and sodium molybdate di-hydrate and water. The secondcompound may be a mixture of mineral acids and an antiscalant polymer.The antiscalant polymer may be polyacrylic acid or a polymeric compound.

[0009] According to an aspect of the invention, a catalyst is used toenhance conversion of the sodium chlorite into an active biocide,chlorine dioxide. By way of typical and therefore non limitive example,the catalyst may be sodium molybdate.

[0010] Other objects, advantages and features of the invention willbecome apparent from the description of the best mode set forth below,from the drawing, from the claims and from the principles that areembodied in the specific structures, compositions and method steps thathave been illustrated and described.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0011] The drawing is a flow diagram of a water distribution system andequipment for preparing the composition of the invention and introducingit into the water system.

DETAILED DESCRIPTION OF THE INVENTION

[0012] The drawing shows, by way of example, a portion of an irrigationsystem that includes a flow meter 10 in a conduit 12, e.g. an irrigationpipe. The flow meter 10 measures the flow in the conduit 12 andgenerates an electrical control signal that is proportional to the flow.The electrical signal may be electrical pulses that are sent to a pulsedivider 14 which generates electrical control signals that are sent tocontrollers for two chemical feed pumps 16, 18. The electrical signalsfrom pulse divider 14 may be electrical pulses which control the pumps16, 18 for proportionally pumping the two components that are mixed.Preferably, the pumps 16, 18 are positive displacement pumps thatinclude pistons. The control signals control the movement of thepistons. Each pumping stroke sends a predetermined volume of chemicalinto a conduit 20, 22 leading from a pump 16, 18 to a reaction chamber24. Pump 16 pumps a first solution or component from its storage tank 26to the reaction chamber 24. Pump 18 pumps a second solution or componentfrom its storage tank 28 to the reaction chamber 24. The two solutionsare precursor chemicals that are allowed to intermingle or react for theperiod of time, e.g. ten or more minutes, in the reaction chamber 24.The reacted mixture is removed through the top of the reaction chamber24 and is delivered by a conduit 30 into the water conduit 12, intoadmixture with water that is flowing through the conduit 12. Theadmixture of the reacted solution in the water substantially instantlydilutes the reacted mixture to a desired working concentration fordistribution by conduit 12 throughout the water system.

[0013] By way of example, the flow sensor may be a Module IP115 hot-tapinsertion flow sensor, manufactured by Sea Metrics, Inc., having abusiness address of 20419 80^(th) Ave.S., Kent, 98032. The pulse dividermay be a model PD10 pulse divider, also manufactured by Sea Metrics,Inc. The pumps may be model B711-392SI pumps manufactured by LMI MiltonRoy, having a business address of 8 Post Office Square, Acton Mass.01720. The reaction chamber 24 may be an off the shelf item. It may bewhat is known as a reaction column that is made from schedule 80PVCpipe, measuring two inches in diameter, and twelve inches long, with endcaps and tubing fittings.

[0014] The pumps 16, 18 force the reactants into the bottom of thereaction chamber or column. The pressure of the pumps 16, 18 forces thereacted mixture up out of the top of the reaction chamber 24, followingbetween ten to twenty minutes admixing time of the reactants in thereaction chamber 24. The pumps 16, 18 are 1.6 gallon per hour capacitypumps.

[0015] The following are some examples that are submitted for thepurpose of making it easier to understand the invention.

EXAMPLE 1

[0016] A solution containing 17.5% wt/wt of PBTC, 0.1% wt/wt sodiummolybdate di-hydrate (Na₂MoO₄:2H₂O) in water was added to an equalvolume of 7.5% wt/wt sodium chlorite (NaCIO₂) in water. After allowingthe mixture to react for ten minutes, small aliquots were added to aliter of stirred irrigation water from a berry farm until the chlorinedioxide level reached 0.5 parts per million. After fifteen minutes,samples were taken for enumeration of bacteria on aerobic plate countagar. Approximately a 10,000 fold reduction in bacteria was achievedbased on the initial bacterial content of the untreated irrigationwater. Water samples treated with only the PBTC solution showed nodecrease in bacterial counts.

EXAMPLE 2

[0017] An irrigation system at a California vineyard carrying 1500gallons per minute of water was treated with the chemical composition inExample 1 resulting in a final concentration of 0.2 ppm chlorine dioxideand 0.8 ppm PBTC. After several days, the bacterial counts increased dueto dispersion and dislodging of established biofilms in the system.However, within a week of continuous treatment, the bacterial countsdecreased 100 fold from the initial level of approximately 1000organisms per ml to less than 10.

EXAMPLE 3

[0018] A sample of irrigation water heavily contaminated with ironrelated bacteria (IRB), a major source of bio-fouling was treated withthe solution of Example 1 to achieve a chlorine dioxide residual of 0.25ppm. After a fifteen minute contact time, the treated water was analyzedfor IRB using the BART (Biological Activity Reaction Test) test kit soldby Droycon Bioconcepts, Inc., Regina, Saskatchewan, Canada. All tracesof IRB were eliminated vs. the control untreated water, which containedan estimated IRB level of 1,000 per ml.

[0019] One component of the reacted mixture may be sodium chlorite.Under acidic conditions this compound spontaneously forms chlorinedioxide, a powerful antimicrobial. Salts of hypochlorite or chlorine gasmay be used in place of the sodium chlorite. This compound may be usedto prepare hypochlorous acid in the reaction chamber 24. This reactedmixture is also a powerful antimicrobial. The second component may be anorganophosphorate compound such as 2-phosphonobutane-1,2,4-tricaboxylicacid (PBTC), CAS Registry No. 37971-36-1. Alternatively, the secondcomponent may be a mixture of mineral acids and antiscalant polymerssuch as polyacrylic acid or other polymeric compounds. The secondcomponent has the attributes of being acidic enough to convert sodiumchlorite into chlorine dioxide while remaining unaffected in thereaction mixture. At the same time it is an excellent mineralantiscalant.

[0020] Very few chelants and/or antiscaling compounds remain unaffectedin the presence of even dilute amounts of oxidizing compounds. PBTC isone of the very few chelants that demonstrates acceptable stability inthe presence of strong oxidizers. Furthermore, the reaction of PBTC withsodium chlorite might be greatly accelerated and reaction time greatlyreduced, by the inclusion of small amounts of a catalyst such as, butnot limited to, sodium molybdate in the PBTC component prior to admixingit with the sodium chlorite component.

[0021] According to an aspect of the invention, the generation anddelivery of antiscalant, antimicrobial mixture is easily achievedon-site by metering the individual component solutions into the reactionvessel 24, either by positive pumping or by vacuum eduction, andintroducing the resultant reaction mixture into the water stream orvolume. In some installations, the reaction mixture may be introducedinto a body of water in a tank as opposed to flowing water in a conduit.

[0022] The process of generating and delivering the reaction mixture maybe conducted intermittently by use of timer controlled chemical feedpumps, or can be conducted continuously, by flow controlled pumping oreduction. Optimum conversion of the sodium chlorite compound into activechlorine dioxide requires at least several minutes of reaction time and,preferably, the use of a suitable catalyst, such as sodium molybdate.Accordingly, the reaction or mixing chamber 24 should be of a suitablevolume to allow the two solutions or components to co-mingle and reactfor the desired length of time before exiting the reaction chamber 24,into the conduit 12 or a water tank.

[0023] The illustrated embodiment is only a single example of thepresent invention and, therefore, is non-limitive. It is to beunderstood that many changes in the particular structure, materials andfeatures of the invention may be made without departing from the spiritand scope of the invention. Therefore, it is our intention that ourpatent rights not be limited by the particular embodiment that isillustrated and described herein, but rather is to be determined by thefollowing claims, interpreted according to accepted doctrines of claiminterpretation, including use of the doctrine of equivalents.

What is claimed is:
 1. A method of treating water in a waterdistribution system, comprising: admixing a sodium chlorite solutionwith a second solution containing an acid to make a reacted mixture; andintroducing a predetermined amount of the reacted mixture into a watersystem.
 2. The method of claim 1, comprising introducing the reactedmixture into the water to inhibit and/or eliminate bacterial fouling inthe system.
 3. The method of claim 1, comprising introducing theactivated mixture into the water for inhibiting and/or removing mineraldeposits from the system.
 4. The method of claim 2, comprisingintroducing the activated mixture into the water for inhibiting and/orremoving mineral deposits from the system.
 5. The method of claim 1,comprising introducing the activated mixture into the water for reducingor eliminating microorganisms from the system.
 6. The method of claim 2,comprising introducing the activated mixture into the water for reducingor eliminating microorganisms from the system.
 7. The method of claim 3,comprising introducing the activated mixture into the water for reducingor eliminating microorganisms from the system.
 8. The method of claim 4,comprising introducing the activated mixture for reducing or eliminatingmicroorganisms from the system.
 9. The method of claim 1, wherein thesecond component is acidic enough to convert the sodium chlorite intochlorine dioxide while remaining unaffected in the reacted mixture andat the same time being a mineral antiscalant.
 10. The method of claim 1,wherein the second solution is formed by adding2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) and sodium molybdatedi-hydrate and water.
 11. The method of claim 1, wherein the secondcompound contains PBTC.
 12. The method of claim 1, wherein the secondcompound is a mixture of mineral acids and antiscalant polymers.
 13. Themethod of claim 12, wherein the antiscalant polymer is polyacrylic acid.14. The method of claim 12, wherein the anticscalant polymer is apolymeric compound.
 15. The method of claim 1, wherein the secondcompound has the attributes of being acidic enough to convert sodiumchlorite into chlorine dioxide while remaining unaffected in thereaction mixture.
 16. The method of claim 1, further comprising using anantiscalant, dispersant compound, as an acid activator, to enhance theproperties of the reacted mixture towards controlling mineral depositsin the water system.
 17. The method of claim 16, further comprisingusing a catalyst to enhance conversion of the sodium chlorite into anactive biocide, chlorine dioxide.
 18. The method of claim 17, whereinthe catalyst is sodium molybdate.
 19. A reacted mixture resulting fromadmixing a sodium chlorite solution with a second solution containing anacid to make the reacted mixture.
 20. The composition of claim 19,wherein the composition will inhibit and/or eliminate bacterial foulingintroduced into a water system.
 21. The composition of claim 19, whereinthe composition will inhibit and/or remove mineral deposits from thewater system.
 22. The composition of claim 19, wherein the compositionwill inhibit and/or remove mineral deposits when introduced into a watersystem.
 23. The composition of claim 19, wherein the composition willreduce and/or eliminate microorganisms from a water system whenintroduced into the water system.
 24. The composition of claim 19,wherein the second component is acidic enough that it will convert thesodium chlorite into chlorine dioxide while remaining unaffected in thereacted mixture and at the same time will be a mineral antiscalant.